Design of the Alkali-Metal-Doped WO₃ as a Near-Infrared Shielding Material for Smart Window

Development of new WO₃-based material is significantly important for smart-window applications. In this work, the electronic properties of alkali metals monodoped (A_0.083WO₃, A = Li, Na, K, Rb, and Cs) and codoped (Li_0.083A_0.083WO₃, A = Li, Na, K, Rb, and Cs) hexagonal WO₃ (hex-WO₃) were investigated by employing the hybrid functional method. It is found that codoping is more stable than monodoping except in the case of (Li, Li). In the monodoped and codoped systems, the Fermi level moves into the conduction band and shows metal-like characteristic, which is responsible for the optical absorption in the visible light and NIR absorption range. In addition, the codoped systems exhibit strong NIR absorption which is not found in the pure hex-WO₃. Our results show that (Li, Cs) codoped hex-WO₃ is the most stable among these systems, showing excellent NIR-shielding property, which is promising for energy-saving smart-window applications